Thursday, April 26, 2012

Evolution Report

There
are thousands of mythologies that explain how life was created and got
onto the earth. Just about every group of people that ever lived made up
some explanation about the creation of life. Because their memory of
history only extended back to the memory of the oldest living person in
the tribe, they had no perspective on how the Earth had changed on
vastly longer time scales. Memory can only last as long as someone
remembers the story. And as anyone knows that has ever played a game of
telephone, the story grows in the telling. The big points stay similar,
but the details are filled in.These
creation stories were comforting for the people who shared them. But as
the dark ages ended Europeans began to chart the course of the stars in
the heavens, systematically dig into the earth, began to explore the
world on ships, and most importantly of all, began to methodically
record the information they were finding, and sharing this information
with others. The information they were finding didn't match the creation
myths to this point. Instead of the Earth being thousands of years old,
life was millions of years old, and then billions of years old. Instead
of the Earth being the center of the universe, the Earth circled around
the Sun, and it wasn't even the biggest planet.This
new evidence completely disproved all the ancient myths. The old ways
of thinking were so entrenched that anyone who disagreed with them was
stoned or burned to death. A new more systematic way of asking questions
about everything was developed called “The Scientific Method.” This
allowed people to ask questions about the universe and experiment to see
if the question was true or not. Instead of taking things on faith this
new method required people to repeat the experiment before they
accepted the theory as true. And new theories could be presented to
refine or replace older theories, without anyone being burned to death.Many
theories were proposed that explained bits and pieces of the theory of
life. One theory took precedence over all the rest. A man named Darwin
took a voyage on a ship and studied a group of islands with an amazing
diversity of life. He noticed many patterns and over the course of years
he worked on a book. Another man named Wallace independently came up
with nearly identical theories to Darwin. So Darwin was forced to
abandon work on his masterwork book and immediately publish a pamphlet
called, “On the Origin of Species.”It
took decades of experiments to prove this controversial work to be
correct. A combination of the study of fossils and looking at living
species. Over the years since then the theory has been refined, but
never disproven.The
way evolution works is that living populations have environmental
pressures. Their offspring will either be fit to survive in that
environment or not. Because there are limited resources the offspring
that can get the most resources and have the most offspring will have
the most descendants, crowding out the less fit. This pressure from
other species and your own species is a form of environmental pressure
as well.It
is important to realize that individuals in a population do not evolve.
The offspring of a pairing can have a lot of different combinations of
genes, which make them more or less fit. Sometimes there is an error
when the DNA is duplicated. Most of the time this causes the offspring
to be completely unfit. But the mutation can result in an individual
that is more fit for the environment it finds itself in.The
pressures of all the species in an area all evolving together is called
macro-evolution. When one species becomes more fit for the environment
it puts more pressure on the other species competing for the same
resources.A
new species forms when individuals from the same species stop breeding
together, either because of behavior changes, or because of geographic
separation. At some point in the future the small changes accumulate or
the number of genes changes and makes it impossible for the individuals
to breed together anymore.We
talked about theories about how life evolves, but where did life
originally come from? Nobody knows for sure, and it is impossible to
prove one way or another. The most popular theory is that the early
atmosphere rained out organic compounds into the early seas and ponds.
Then primitive replicating molecules began duplicating. Eventually a
cell wall was formed by mistake, this became the primary cell that out
competed all the existing self replicating molecules.This
cell replicated itself and mutations caused it to fit into every
available ecological niches. Cells began to invade other cells in
parasitic relationships. Eventually these relationships became symbiotic
and beneficial to both cells. This happened several times; once with
mitochondria, a second time with the nucleus replacing previous, and a
third time with chloroplasts. This increase in complexity allowed the
development of multi-cellular life. This multi-cellular life got washed
up onto land during high tide, became adapted for land bit by bit, and
then spread from the shore inland.If
you look at all the stellar systems in our galaxy, and all the galaxies
in the sky, the odds that life evolved on more than just one planet is
almost a certainty. Even if you say that only 1 in a million suns has a
planet in the right place, and 1 in a million of those planets develop
life, that still leaves millions of places that life could develop. And
life may just be completely adaptable so that it can form in conditions
well beyond what we expect, including in interstellar space far from any
sun. We have found life on Earth in ice fields, miles deep in the
earth, miles deep under the ocean around volcanic vents, in hot springs,
and even in nuclear reactors. It may be possible that the first life on
Earth came from the comets that rained down onto the forming planet.